Mutant factor viii compositions and methods

ABSTRACT

In one aspect, present invention provides a recombinant mutant human factor VIII having increased expression and/or secretion as compared to wild-type factor VIII. In certain embodiments, the recombinant factor VIII includes one or more amino acid substitution(s) selected from the group consisting of I86, Y105, A108, D115, Q117, F129, G132, H134, M147 and L152. In other aspects, the present invention provides FVIII encoding nucleic acids, FVIII-expression vectors, as well as methods of using the modified FVIII genes in the treatment of FVIII deficiencies, such as hemophilia A.

This application claims priority to U.S. Provisional Patent Application Ser. No. 61/838,867, filed on Jun. 24, 2013. The entirety of the aforementioned application is incorporated herein by reference.

GOVERNMENT LICENSE RIGHTS

This invention was made with U.S. Government support under grant HL084381 from the National Institutes of Health. The U.S. Government thus may have certain license rights in this invention.

FIELD

The present invention relates to recombinant human factor VIII mutants exhibiting higher expression levels than the corresponding wild-type human factor VIII. The present invention also relates to methods of making and using the recombinant human factor VIII mutants.

BACKGROUND

Hemophilia A, the most common of the severe, inherited bleeding disorders, results from a deficiency or defect in the plasma protein factor VIII. In patients with Hemophilia A, the blood does not clot properly resulting in excessive bleeding when the hemophiliac is injured. Treatment consists of replacement therapy using preparations of (purified) plasma or the recombinant protein.

Blood clotting begins when platelets adhere to the cut wall of an injured blood vessel at a lesion site. Subsequently, in a cascade of enzymatically regulated reactions, soluble fibrinogen molecules are converted by the enzyme thrombin to insoluble strands of fibrin that hold the platelets together in a thrombus. At each step in the cascade, a protein precursor is converted to a protease that cleaves the next protein precursor in the series. Cofactors are required at most of the steps.

Factor VIII circulates as an inactive, non-covalent, metal ion-dependent heterodimer precursor in blood, bound tightly and non-covalently to von Willebrand factor. This procofactor form of the protein contains a heavy chain (HC) comprised of A1(a1)A2(a2)B domains and a light chain (LC) comprised of (a3)A3C1C2 domains, with the lower case a representing short (˜30-40 residue) segments rich in acidic residues. Factor VIII is proteolytically activated by proteolytic cleavages at the A1A2, A2B and A3A3 junctions catalyzed by thrombin or factor Xa, which serves to dissociate it from von Willebrand factor and activate its procoagulant function in the cascade. In its active form, the protein factor VIIIa is a cofactor that increases the catalytic efficiency of the serine protease factor IXa in the membrane-dependent conversion of zymogen factor X to the serine protease, factor Xa factor by several orders of magnitude.

Gene therapy has been proposed as treatment modality for supplementing deficiencies in clotting factors in hemophiliacs and there have been attempts to engineer FVIII constructs that are suitable for treatment of humans. For example, Connelly, et al. reported that treatment of FVIII-deficient mice with human FVIII-encoding adenoviral vectors resulted in expression of biologically active human FVIII (Connelly, et al., Blood, Vol. 91, No. 9 (1998), pp. 3273-3281). Sarkar, et al. reported that use of AAV8 serotype in combination with FVIII corrected plasma FVIII activity in mouse models (Sarkar, et al., Blood, Vol. 103, No. 4 (2004), pp. 1253-1260).

However, as in many areas of gene therapy, theory is much more straightforward than successful, effective implementation. Difficulties in implementation of gene therapy techniques include problems encountered in the use of viruses as gene vectors and insufficient expression levels of FVIII. For example, human FVIII secretes very inefficiently and the yield is logs lower comparing to similar proteins such as factor V. Further, while viruses are effective as gene vectors because they can be used to transduce cells leading to protein expression in vivo, the proteins coating the virus particle may activate the body's immune system.

Thus, in view of the foregoing, there is a need for approaches that can efficiently express the target FVIII protein in sufficient quantity to reduce the required dose of viral vector to tolerable levels.

SUMMARY

The present invention provides modified factor VIII (FVIII) proteins, FVIII encoding nucleic acids, and FVIII-expression vectors, as well as methods of using the modified FVIII genes in the treatment of FVIII deficiencies, such as hemophilia A.

In one aspect, present invention provides a mutant human factor VIII having increased expression or secretion as compared to wild-type factor VIII.

In one embodiment, the recombinant mutant human factor VIII includes one or more amino acid substitution(s) selected from the group consisting of I86, Y105, A108, D115, Q117, F129, G132, H134, M147, L152 and combinations thereof.

In another embodiment, the recombinant mutant human factor VIII includes one or more amino acid substitution(s) selected from the group consisting of I86V, Y105F, A108S, D115E, Q117H, F129L, G132K, H134Q, M147T, L152P and combinations thereof.

In another embodiment, the recombinant mutant human factor VIII includes amino acid substitutions in each of the amino acids I86, Y105, A108, D115, Q117, F129, G132, H134, M147 and L152.

In another embodiment, the recombinant mutant human factor VIII includes the amino acid substitutions I86V, Y105F, A108S, D115E, Q117H, F129L, G132K, H134Q, M147T and L152P.

In another embodiment, the recombinant mutant human factor VIII includes one or more amino acid substitution(s) selected from the group consisting of I86, A108, G132, M147, L152 and combinations thereof.

In another embodiment, the recombinant mutant human factor VIII includes one or more amino acid substitution(s) selected from the group consisting of I86V, A108S, G132K, M147T, L152P and combinations thereof.

In another embodiment, the recombinant mutant human factor VIII includes amino acid substitutions in each of I86V, A108S, G132K, M147T and L152P.

In another embodiment, the recombinant mutant human factor VIII includes the amino acid substitutions I86V, A108S, G132K, M147T and L152P.

In other embodiments, the human factor VIII mutants further include a deletion in the B domain of human factor VIII.

In other embodiments, the human factor VIII mutants further include the a2 and/or a3 domain(s) of human factor VIII.

In another aspect, the present invention provides isolated polynucleotide sequences encoding the human factor VIII mutants described herein.

In yet another aspect, the present invention provides an expression vector operatively linked to the polynucleotides encoding the human factor VIII mutants described herein.

In a further aspect, the present invention provides a pharmaceutical composition comprising an expression vector operatively linked to the polynucleotides encoding the human factor VIII mutants described herein.

In another aspect, the present invention provides a method for treating a patient with a factor VIII deficiency comprising administering to a patient in need thereof a pharmaceutical composition comprising an expression vector operatively linked to the polynucleotides encoding a human factor VIII mutant described herein in an amount effective for treating the factor VIII deficiency.

In yet another aspect, the present invention provides a method for expressing a human factor VIII polypeptide mutant comprising: (a) transforming a host cell with an expression vector operatively linked to a polynucleotides encoding a human factor VIII mutant according to the present invention; (b) growing the host cell under conditions suitable for expressing the human factor VIII polypeptide mutant; and (c) purifying the human factor VIII polypeptide mutant from host cells expressing said mutant.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates the structural domains of the human factor VIII heavy and light chains, including several heavy chain constructions utilized in the present invention.

FIG. 2 is a graph showing an alignment of the first 200 amino acids of the secreted human factor VIII heavy chain alongside a modified factor VIII with 10 exemplary substitutions for enhanced secretion.

FIG. 3 is a graph showing the alignment of the first 200 amino acids of the secreted human factor VIII heavy chain alongside a modified human factor VIII mutant with 5 exemplary substitutions for enhanced secretion.

FIG. 4 summarizes exemplary amino acids determined to affect human factor VIII secretion.

FIGS. 5 and 6 depict exemplary AAV vectors for expressing B-domain deleted human factor VIII mutants or human factor VIII heavy chain.

FIG. 7 shows a comparison of the secretion of different human factor VIII mutants in BHK cells (panel A) or 293 cells (panel B).

FIG. 8 shows a comparison of the secretion of different human factor VIII mutants in secretion in vivo. Plasmids pAAV-CB-hBDDF8 (carrying human factor VIII with B-domain deleted), pAAV-CB-hBDDF8-X10 (carrying hF8-BDD with 10 substitutions), pAAV-CB-hBDD-F8-X5 (carrying hBDDF8 with 5 substitutions) or pAAV-CB-hBDD-F8-G312K (hF8 with G132K substitutions) were injected in factor VIII double knock-out Blab/c mice.

FIG. 9 show a comparison of the secretion of different human factor VIII mutants in 293 cells Amino acids in hBDD-F8-X10 were reverted back to their corresponding wild type amino acids. In hBDD-F8-X10-6p, 6 of 10 amino acids in hBDD-F8-X10 differing from wild type F8 were reverted back to their wild type amino acids.

FIG. 10 shows a comparison of the expression and secretion of a mutant factor VIII (F8) heavy chain (HC1690-X10) in an AAV vector construct with a wild type hF8-HC1690 AAV vector construct (AAV/hF8HC1690) in vivo.

FIG. 11 shows a comparison of the secretion of different G132 factor VIII heavy chain mutants in 293 cells.

FIG. 12 shows a comparison of the secretion of different factor VIII heavy chain mutants in expression/secretion in factor VIII double knock-out Blab/c mice.

FIG. 13 shows a comparison of the secretion of different L152 factor VIII heavy chain mutants in 293 cells.

FIG. 14 shows a comparison of the secretion of different A108 factor VIII heavy chain mutants in 293 cells.

FIG. 15 shows a comparison of the secretion of different M147 factor VIII heavy chain mutants in 293 cells.

FIG. 16 shows that there was no formation of neutralizing antibodies against 5 mutated amino acids in the F8−/− rat model.

DETAILED DESCRIPTION

Various terms relating to the biological molecules of the present invention are used hereinabove and also throughout the specification and claims.

The phrase “secretion enhanced factor VIII (seFVIII, seF8)” refers to a modified FVIII (F8) which has been genetically altered such that the encoded protein exhibits at least 10% or 20% or 50% or 100% increase in secretion when compared to unmodified FVIII. The nucleotide sequences described herein are readily obtainable from GenBank. For human FVIII, see Accession No. NG-011403.1.

The phrase “BDD” refers to a “B-domainless” factor VIII (F8 or FVIII) mutant lacking the B domain.

The phrase “one or more” followed by a list of elements or species is intended to encompass any permutation of elements or species in the list. Thus, for example, the phrase “one or more substitution mutations selected from the group consisting of A, B, C, D, E and F” may include any combination of substitution mutations containing A, B, C, D, E and/or F.

As used herein, ranges may be expressed from one particular integer value to another particular integer value. When such a range is expressed, it should understand that any and all integer values within that range define separate embodiments according to the present invention and that the full scope of embodiments includes within the range further includes any and all sub-ranges between any pair of integer values in the initial range.

With reference to nucleic acids of the invention, the term “isolated nucleic acid”, when applied to DNA, refers to a DNA molecule that is separated from sequences with which it is immediately contiguous (in the 5′ and 3′ directions) in the naturally occurring genome of the organism from which it originates. For example, the “isolated nucleic acid” may comprise a DNA or cDNA molecule inserted into a vector, such as a plasmid or virus vector, or integrated into the DNA of a prokaryote or eukaryote. The nucleic acid codons can be optimized for enhanced expression in the mammalian cells.

With respect to RNA molecules of the invention, the term “isolated nucleic acid” primarily refers to an RNA molecule encoded by an isolated DNA molecule as defined above. Alternatively, the term may refer to an RNA molecule that has been sufficiently separated from RNA molecules with which it would be associated in its natural state (i.e., in cells or tissues), such that it exists in a “substantially pure” form (the term “substantially pure” is defined below).

With respect to protein, the term “isolated protein” or “isolated and purified protein” is sometimes used herein. This term refers primarily to a protein produced by expression of an isolated nucleic acid molecule of the invention. Alternatively, this term may refer to a protein which has been sufficiently separated from other proteins with which it would naturally be associated, so as to exist in “substantially pure” form.

The term “promoter region” refers to the transcriptional regulatory regions of a gene, which may be found at the 5′ or 3′ side of the coding region, or within the coding region, or within introns.

The term “vector” refers to a small carrier DNA molecule into which a DNA sequence can be inserted for introduction into a host cell where it will be replicated. An “expression vector” is a specialized vector that contains a gene or nucleic acid sequence with the necessary regulatory regions needed for expression in a host cell.

The term “operably linked” means that the regulatory sequences necessary for expression of a coding sequence are placed in the DNA molecule in the appropriate positions relative to the coding sequence so as to effect expression of the coding sequence. This same definition is sometimes applied to the arrangement of coding sequences and transcription control elements (e.g., promoters, enhancers, and termination elements) in an expression vector. This definition is also sometimes applied to the arrangement of nucleic acid sequences of a first and a second nucleic acid molecule wherein a hybrid nucleic acid molecule is generated.

The term “substantially pure” refers to a preparation comprising at least 50-60% by weight the compound of interest (e.g., nucleic acid, oligonucleotide, protein, etc.). More preferably, the preparation comprises at least 75% by weight, and most preferably 90-99% by weight, of the compound of interest. Purity is measured by methods appropriate for the compound of interest (e.g., chromatographic methods, agarose or polyacrylamide gel electrophoresis, HPLC analysis, and the like).

The phrase “consisting essentially of” when referring to a particular nucleotide sequence or amino acid sequence means a sequence having the properties of a given SEQ ID NO. For example, when used in reference to an amino acid sequence, the phrase includes the sequence per se and molecular modifications that would not affect the basic and novel characteristics of the sequence.

The term “oligonucleotide,” as used herein refers to primers and probes of the present invention, and is defined as a nucleic acid molecule comprised of two or more ribo- or deoxyribonucleotides, preferably more than three. The exact size of the oligonucleotide will depend on various factors and on the particular application for which the oligonucleotide is used. The term “probe” as used herein refers to an oligonucleotide, polynucleotide or nucleic acid, either RNA or DNA, whether occurring naturally as in a purified restriction enzyme digest or produced synthetically, which is capable of annealing with or specifically hybridizing to a nucleic acid with sequences complementary to the probe. A probe may be either single-stranded or double-stranded. The exact length of the probe will depend upon many factors, including temperature, source of probe and method of use. For example, for diagnostic applications, depending on the complexity of the target sequence, the oligonucleotide probe typically contains 15-25 or more nucleotides, although it may contain fewer nucleotides.

The term “percent identical” is used herein with reference to comparisons among nucleic acid or amino acid sequences. Nucleic acid and amino acid sequences are often compared using computer programs that align sequences of nucleic or amino acids thus defining the differences between the two. Comparisons of nucleic acid sequences may be performed using the GCG Wisconsin Package version 9.1, available from the Genetics Computer Group in Madison, Wis. For convenience, the default parameters (gap creation penalty=12, gap extension penalty=4) specified by that program are intended for use herein to compare sequence identity. Alternately, the Blastn 2.0 program provided by the National Center for Biotechnology Information (found on the world wide web at ncbi.nlm.nih.gov/blast/; Altschul, et al., 1990, J Mol Biol 215:403-410) using a gapped alignment with default parameters, may be used to determine the level of identity and similarity between nucleic acid sequences and amino acid sequences.

A “corresponding” nucleic acid or amino acid or sequence of either, as used herein, is one present at a site in a factor VIII or hybrid factor VIII molecule or fragment thereof that has the same structure and/or function as a site in the factor VIII molecule of another species, although the nucleic acid or amino acid number may not be identical. A sequence “corresponding to” another factor VIII sequence substantially corresponds to such sequence, and hybridizes to the human factor VIII DNA sequence designated SEQ ID NO:1 under stringent conditions. A sequence “corresponding to” another factor VIII sequence also includes a sequence that results in the expression of a factor VIII or claimed procoagulant hybrid factor VIII or fragment thereof and would hybridize to a nucleic molecule comprising SEQ ID NO:1 but for the redundancy of the genetic code.

A “unique” amino acid residue or sequence, as used herein, refers to an amino acid sequence or residue in the factor VIII molecule of one species that is different from the homologous residue or sequence in the factor VIII molecule of another species.

“Specific activity,” as used herein, refers to the activity that will correct the coagulation defect of human factor VIII-deficient plasma. Specific activity is measured in units of clotting activity per milligram total factor VIII protein in a standard assay in which the clotting time of human factor VIII deficient plasma is compared to that of normal human plasma. One unit of factor VIII activity is the activity present in one milliliter of normal human plasma. In the assay, the shorter the time for clot formation, the greater the activity of the factor VIII being assayed. Hybrid human/porcine factor VIII has coagulation activity in a human factor VIII assay. This activity, as well as that of other hybrid or hybrid equivalent factor VIII molecules or fragments thereof, may be less than, equal to, or greater than that of either plasma-derived or recombinant human factor VIII.

“Subunits” of human or animal factor VIII, as used herein, are the heavy and light chains of the protein. The heavy chain of factor VIII contains three domains, A1, A2, and B. The light chain of factor VIII also contains three domains, A3, C1, and C2.

The terms “epitope”, “antigenic site”, and “antigenic determinant”, as used herein, are used synonymously and are defined as a portion of the human, animal, hybrid, or hybrid equivalent factor VIII or fragment thereof that is specifically recognized by an antibody. It can consist of any number of amino acid residues, and it can be dependent upon the primary, secondary, or tertiary structure of the protein. In accordance with this disclosure, a hybrid factor VIII, hybrid factor VIII equivalent, or fragment of either that includes at least one epitope may be used as a reagent in the diagnostic assays described below. In some embodiments, the hybrid or hybrid equivalent factor VIII or fragment thereof is not cross-reactive or is less cross-reactive with all naturally occurring inhibitory factor VIII antibodies than human or porcine factor VIII.

The term “immunogenic site”, as used herein, is defined as a region of the human or animal factor VIII, hybrid or hybrid equivalent factor VIII, or fragment thereof that specifically elicits the production of antibody to the factor VIII, hybrid, hybrid equivalent, or fragment in a human or animal, as measured by routine protocols, such as immunoassay, e.g., ELISA, or the Bethesda assay, described herein. It can consist of any number of amino acid residues, and it can be dependent upon the primary, secondary, or tertiary structure of the protein. In some embodiments, the hybrid or hybrid equivalent factor VIII or fragment thereof is nonimmunogenic or less immunogenic in an animal or human than human or porcine factor VIII.

“Factor VIII deficiency,” as used herein, includes deficiency in clotting activity caused by production of defective factor VIII, by inadequate or no production of factor VIII, or by partial or total inhibition of factor VIII by inhibitors. Hemophilia A is a type of factor VIII deficiency resulting from a defect in an X-linked gene and the absence or deficiency of the factor VIII protein it encodes.

In one aspect, the present invention relates to a recombinant factor VIII mutant molecule (e.g., protein or nucleic acid) characterized by increased expression and/or secretion as compared to wild-type factor VIII.

Exemplary human factor VIII cDNA (nucleotide) and predicted amino acid sequences are shown in SEQ ID NOs: 1 and 2, respectively. Human factor VIII is synthesized and secreted as an approximately 300 kDa single chain protein of 2332 amino acids with internal sequence homologies defining a series of structural “domains” as follows: NH₂-A1-a1-A2-a2-B-a3-A3-C1-C2-COOH (FIG. 4). As used herein, a factor VIII “domain” is defined by a continuous sequence of amino acids characterized by e.g., internal amino acid sequence identity to structurally related domains and by sites of proteolytic cleavage by thrombin. Further, the terms “domainless” or “lacking a domain” should be understood to mean that at least 95% or 100% of the domain has been deleted. Unless otherwise specified, factor VIII domains are defined by the following amino acid residues in the human factor VIII amino acid sequence set forth in SEQ ID NO:2:

A1, residues A1a1-Arg372

A2, residues Ser373-Arg740

B, residues Ser741-Arg1648;

a3, residues P1640-Arg1649;

A3, residues Ser1690-Ile2032;

C1, residues Arg2033-Asn2172; and

C2, residues Ser2173-Tyr2332

The A3-C1-C2 sequence includes residues Ser1690-Tyr2332. The remaining sequence, residues Glu1649-Arg1689, is usually referred to as the factor VIII light chain activation peptide (FIG. 1). Factor VIII is proteolytically activated by thrombin or factor Xa, which dissociates it from von Willebrand factor, forming factor VIIIa, which has procoagulant function. The biological function of factor VIIIa is to increase the catalytic efficiency of factor IXa toward factor X activation by several orders of magnitude. Thrombin-activated factor VIIIa is a 160 kDa A1/A2/A3-C1-C2 heterotrimer that forms a complex with factor IXa and factor X on the surface of platelets or monocytes.

A cDNA sequence encoding the wild-type human factor VIII has the nucleotide sequence set forth in SEQ ID NO:1. In SEQ ID NO:1, the first 57 nucleotides of the factor VIII open reading frame encodes a signal peptide sequence which is typically cleaved off from the mature factor VIII protein represented by SEQ ID NO:2.

Preferred recombinant factor VIII mutants include or encode one or more amino acid substitutions in the region from aa 86 to aa 152 of the wild-type human factor VIII amino acid sequence set forth in SEQ ID NO:2. Substitutions within any of these positions may employ any of the other 19 amino acids.

With reference to mutants described herein, the notion represented by “(amino acid a)-(SEQ ID NO:2 amino acid #b)-(amino acid c)” should be understood to mean that wild type amino acid a (one-letter code) at amino acid number b of SEQ ID NO:2 has been mutated to amino acid c.

In certain preferred embodiments, the human factor VIII polypeptide mutant comprises amino acid substitution(s) in one or more amino acids in SEQ ID NO:2 selected from the group consisting of I86, Y105, A108, D115, Q117, F129, G132, H134, M147 and L152. Further, the human factor VIII mutants may include any permutation of mutations encompassing these ten amino acid sites. Exemplary human factor VIII mutants are described in FIG. 4.

An exemplary recombinant factor VIII of this invention includes a point mutation involving a substitution at I86 of SEQ ID NO:2. A preferred substitution includes valine (i.e., I86V). Further preferred substitutions include leucine (I86L) and methionine (I86M).

Another exemplary recombinant factor VIII includes a point mutation involving a substitution at Y105 of SEQ ID NO:2. The substitution may include any of the other 19 amino acids. Preferred substitutions include Y105F and Y105W.

Another exemplary recombinant factor VIII includes a point mutation involving a substitution of at positions A108 of SEQ ID NO:2. A preferred substitution includes: A108S. Further preferred substitutions include A108S, A108G, A108T and A108P.

Another exemplary recombinant factor VIII includes a point mutation involving a substitution of at positions D115 of SEQ ID NO:2. A preferred substitution includes: D115E. Further preferred substitutions include D115N, D115H, D115Q, D115R and D115K.

Another exemplary recombinant factor VIII includes a point mutation involving a substitution of at positions Q117 of SEQ ID NO:2. A preferred substitution includes: Q117H. Further preferred substitutions include Q117N, Q117E, Q117D, Q117R and Q117K.

Another exemplary recombinant factor VIII includes a point mutation involving a substitution of at positions F129 of SEQ ID NO:2. A preferred substitution include: F129L. Further preferred substitutions include F129V, F129I, F129M, F129P, F129T and F129K.

Another exemplary recombinant factor VIII includes a point mutation involving a substitution of at positions G132 of SEQ ID NO:2. A preferred substitution include: G132K. Further preferred substitutions include G132E, G132D, G132R, G132T, G132M, G132N, G132S and G132W.

Another exemplary recombinant factor VIII includes a point mutation involving a substitution of at positions H134 of SEQ ID NO:2. A preferred substitution includes: H134Q. Further preferred substitutions include H134G, H134Y, H134N, H134E, H134D, H134R and H134K.

Another exemplary recombinant factor VIII includes a point mutation involving a substitution of at positions M147 of SEQ ID NO:2. A preferred substitution includes: M147T. Further preferred substitutions include M147A, M147G, M147S and M147P.

Another exemplary recombinant factor VIII includes a point mutation involving a substitution of at positions L152 of SEQ ID NO:2. A preferred substitution includes: L152P. Further preferred substitutions include L152S, L152G and L152T.

Another exemplary recombinant factor VIII includes multiple substitutions of one or more amino acid residues at positions I86, A108, G132, M147, L152 of SEQ ID NO:2. The substitution(s) can include any permutation of mutations encompassing these five amino acid sites. Specific embodiments may include mutations at one or more substitution mutations selected from the group consisting of I86V, A108S, G132K, M147T, L152P. Further preferred embodiments include 2, 3, 4 or 5 substitutions, including any combination (or permutation) of substitutions selected from I86V, A108S, G132K, M147T and L152P.

Exemplary recombinant factor VIII mutants include point mutation(s) involving substitution(s) at one or more amino acid residues in SEQ ID NO:2 selected from the group consisting of I86, Y105, A108, D115, Q117, F129, G132,14134, M147 and L152. The substitution(s) can include any permutation of mutations encompassing these ten amino acid sites. Specific embodiments may include mutations at one or more substitution mutations selected from the group consisting of I86V, Y105F, A108S, D115E, Q117H, F129L, G132K, H134Q, M147T and L152P. Further preferred embodiments include 2, 3, 4 or up to 9 substitutions, including any combination (or permutation) of substitutions selected from I86V, Y105F, A108S, D115E, Q117H, F129L, G132K, H134Q, M147T and L152P.

The nucleic acids encoding the above mentioned factor VIII substitutions are included in this invention and include all possible nucleic acids encoding the breadth of substitution mutants described herein.

Compared to wild type factor VIII in production (in cell lines or in vivo), the above described factor VIII mutants may exhibit increases in factor VIII secretion of between 5% to 10,000 fold, 10% to 2,000 fold, 50% up to 500 fold, 2 to 200 fold, 5 to 100 fold, 10 to 50 fold, at least 2 fold, at least 5 fold, at least 10 fold, at least 20 fold, at least 50 fold, at least 100 fold, at least 200 fold, at least 500 fold, at least 2,000 fold or at least 10,000 fold.

In certain embodiments, suitable mutant factor VIII sequences may be further modified to include, delete, or modify other factor VIII sequences to confer properties with regard to other attributes, including, without limitation, antigenicity, circulating half-life, protein secretion, affinity for factor IXa and/or factor X, altered factor VIII-inactivation cleavage sites, stability of the activated factor VIII form, immunogenicity, and shelf-life.

In certain specific embodiments, the mutant factor VIII may be modified to produce a B-domain deleted (BDD) or “B-domainless” factor VIII product. FIG. 1 shows an exemplary BDD factor VIII embodiment containing amino acid residues 1-740 and 1690-2332 of SEQ ID NO:2. Preferably, the recombinant B-domainless factor VIII contains one or multiple substitutions at positions I86, Y105, A108, D115, Q117, F129, G132, H134, M147, L152 as described herein.

In one embodiment, a B-domainless recombinant factor VIII is produced, whereby the B-domain is replaced with a DNA linker segment and at least one codon is replaced with a codon encoding an amino acid residue having the same charge as a corresponding residue of porcine factor VIII (see, e.g., U.S. Patent Application Publication No. 2004/0197875 to Hauser, et al.).

In another embodiment, a B-domainless recombinant factor VIII is produced having a truncated factor IX intron 1 inserted in one or more locations (see, e.g., U.S. Pat. No. 6,800,461 to Negrier and U.S. Pat. No. 6,780,614 to Negrier). This recombinant factor VIII can be used for yielding higher production of the recombinant factor VIII in vitro as well as in a transfer vector for gene therapy (see, e.g., U.S. Pat. No. 6,800,461 to Negrier). In a particular embodiment, the recombinant factor VIII can be encoded by a nucleotide sequence having a truncated factor IX intron 1 inserted in two locations and having a promoter that is suitable for driving expression in hematopoietic cell lines, and specifically in platelets (see, e.g., U.S. Pat. No. 6,780,614 to Negrier).

A second example of a suitable mutant factor VIII that can be modified in accordance with the present invention is a chimeric human/animal factor VIII that contains one or more animal amino acid residues as substitution(s) for human amino acid residues that are responsible for the antigenicity of human factor VIII. In particular, animal (e.g., porcine) residue substitutions can include, without limitation, one or more of the following: R484A, R488G, P485A, L486S, Y487L, Y487A, S488A, S488L, R489A, R489S, R490G, L491S, P492L, P492A, K493A, G494S, V495A, K496M, H497L, L498S, K499M, D500A, F501A, P502L, 1503M, L504M, P505A, G506A, E507G, 1508M, 1508A, M2199I, F2200L, L2252F, V2223A, K2227E and/or L2251 (U.S. Pat. No. 5,859,204 to Lollar, U.S. Pat. No. 6,770,744 to Lollar, and U.S. Patent Application Publication No. 2003/0166536 to Lollar). Preferably, the recombinant chimeric factor VIII contains one or multiple substitutions at positions I86, Y105, A108, D115, Q117, F129, G132, H134, M147 and L152 as described herein.

In a further embodiment, the mutant factor VIII is modified to confer greater stability of activated factor VIII by virtue of fused A2 and A3 domains. In particular, a factor VIII can be modified by substituting cysteine residues at positions 664 and 1826, (i.e., Y664C, T1826C) resulting in a mutant factor VIII forming a Cys664-Cys1826 disulfide bond covalently linking the A2 and A3 domains (Gale, et al., “An Engineered Interdomain Disulfide Bond Stabilizes Human Blood Coagulation Factor VIIIa,” J. Thrombosis and Haemostasis 1(9):1966-1971 (2003)). Preferably, the recombinant fused domain (A2-A3) factor VIII contains one or multiple substitutions at positions I86, Y105, A108, D115, Q117, F129, G132, H134, M147 and L152 as described herein.

In a further embodiment, a mutant factor VIII in accordance with the present invention (e.g., containing one or multiple substitutions at positions I86, Y105, A108, D115, Q117, F129, G132, H134, M147 and/or L152) is further modified to confer altered inactivation cleavage sites. For example, Arg336 or Arg562 may be substituted used to decrease the mutant factor VIII's susceptibility to cleavage enzymes that normally inactivate the wild type factor VIII (see, e.g., Amano, et al., “Mutation at Either Arg336 or Arg562 in Factor VIII is Insufficient for Complete Resistance to Activated Protein C (APC)-Mediated Inactivation: implications for the APC Resistance Test,” Thrombosis & Haemostasis 79(3):557-63 (1998)).

In a further embodiment, a mutant factor VIII in accordance with the present invention (e.g., containing one or multiple substitutions at positions I86, Y105, A108, D115, Q117, F129, G132, H134, M147 and/or L152) is further modified to confer enhanced affinity for factor IXa (see, e.g., Fay, et al., “Factor VIIIa A2 Subunit Residues 558-565 Represent a Factor IXa Interactive Site,” J. Biol. Chem. 269(32):20522-7 (1994); Bajaj, et al., “Factor IXa: Factor VIIIa Interaction. Helix 330-338 of Factor IXa Interacts with Residues 558-565 and Spatially Adjacent Regions of the A2 Subunit of Factor VIIIa,” J. Biol. Chem. 276(19):16302-9 (2001); and Lenting, et al., “The Sequence Glu1811-Lys1818 of Human Blood Coagulation Factor VIII Comprises a Binding Site for Activated Factor IX,” J. Biol. Chem. 271(4):1935-40 (1996)) and/or factor X (see, e.g., Lapan, et al., “Localization of a Factor X Interactive Site in the A1 Subunit of Factor VIIIa,” J. Biol. Chem. 272:2082-88 (1997)).

In yet another further embodiment, a mutant factor VIII in accordance with the present invention (e.g., containing one or multiple substitutions at positions I86, Y105, A108, D115, Q117, F129, G132, H134, M147 and/or L152) is further modified to further enhance secretion of factor VIII (see, e.g., Swaroop, et al., “Mutagenesis of a Potential Immunoglobulin-Binding Protein-Binding Site Enhances Secretion of Coagulation Factor VIII,” J. Biol. Chem. 272(39):24121-4 (1997)).

In a further embodiment, a mutant factor VIII in accordance with the present invention (e.g., containing one or multiple substitutions at positions I86, Y105, A108, D115, Q117, F129, G132, H134, M147 and/or L152) is further modified to confer increased circulating half-life. This may be achieved through various approaches, including, without limitation, by reducing interactions with heparan sulfate (Sarafanov, et al., “Cell Surface Heparan Sulfate Proteoglycans Participate in Factor VIII Catabolism Mediated by Low Density Lipoprotein Receptor-Related Protein,” J. Biol. Chem. 276(15):11970-9 (2001)) and/or low-density lipoprotein receptor-related protein (“LRP”) (Saenko, et al., “Role of the Low Density Lipoprotein-Related Protein Receptor in Mediation of Factor VIII Catabolism,” J. Biol. Chem. 274(53):37685-92 (1999); and “The Light Chain of Factor VIII Comprises a Binding Site for Low Density Lipoprotein Receptor-Related Protein,” J. Biol. Chem. 274(34):23734-9 (1999)).

An eighth example of a suitable mutant factor VIII that can be modified in accordance with the present invention is a modified factor VIII encoded by a nucleotide sequence modified to code for amino acids within known, existing epitopes to produce a recognition sequence for glycosylation at asparagine residues (see, e.g., U.S. Pat. No. 6,759,216 to Lollar). Such modification can be useful escaping detection by existing inhibitory antibodies (low antigenicity factor VIII) and decreasing the likelihood of developing inhibitory antibodies (low immunogenicity factor VIII). In one representative embodiment, the modified factor VIII is mutated to incorporate a consensus amino acid sequence for N-linked glycosylation, such as N-X-S/T (see U.S. Pat. No. 6,759,216 to Lollar).

A ninth example of a suitable mutant factor VIII that can be modified in accordance with the present invention is a modified factor VIII that is a procoagulant-active factor VIII having various mutations (see, e.g., U.S. Patent Application Publication No. 2004/0092442 to Kaufman, et al.). One example of this embodiment relates to a modified factor VIII that has been modified to (i) delete the von Willebrand factor binding site, (ii) add a mutation at Arg 740, and (iii) add an amino acid sequence spacer between the A2- and A3-domains, where the amino acid spacer is of a sufficient length so that upon activation, the procoagulant-active factor VIII protein becomes a heterodimer (see U.S. Patent Application Publication No. 2004/0092442 to Kaufman, et al).

Further, the mutant factor VIII can be modified to take advantage of various advancements regarding recombinant coagulation factors generally (see, e.g., Saenko, et al., “The Future of Recombinant Coagulation Factors,” J. Thrombosis and Haemostasis 1:922-930 (2003)).

The recombinant factor VIII of the present invention can be modified at position I86, Y105, A108, D115, Q117, F129, G132, H134, M147, L152, as well as be modified to be B-domainless, to be chimeric, to have fused A2-A3 domains, to have altered inactivation cleavage sites, to have enhanced factor IXa and/or factor X affinity, to have enhanced specific activity, to have an increased circulating half-life, to have mutant glycosylation sites, or to possess any two or more of such modifications in addition to the modifications at position(s) I86, Y105, A108, D115, Q117, F129, G132, H134, M147 and/or L152.

Another aspect of the present invention relates to a method of making a recombinant factor VIII having increased specific activity compared to that of a wild-type factor VIII. This method involves altering the amino acid sequence of a wild-type factor VIII to yield a recombinant factor VIII. Alteration of the amino acid sequence of the wild-type factor VIII can include, for example, introducing at least one point mutation in or near at least one calcium binding site of the wild-type factor VIII. Thereafter, using protein analysis techniques well-known in the art, a determination can be made as to whether the recombinant factor VIII has increased specific activity compared to that of the wild-type factor VIII.

The recombinant factor VIII is preferably produced in a substantially pure form. In a particular embodiment, the substantially pure recombinant factor VIII is at least about 80% pure, more preferably at least 90% pure, most preferably at least 95% pure, 98% pure, 99% pure or 99.9% pure. A substantially pure recombinant factor VIII can be obtained by conventional techniques well known in the art. Typically, the substantially pure recombinant factor VIII is secreted into the growth medium of recombinant host cells. Alternatively, the substantially pure recombinant factor VIII is produced but not secreted into growth medium. In such cases, to isolate the substantially pure recombinant factor VIII, the host cell carrying the recombinant plasmid is propagated, lysed by sonication, heat, or chemical treatment, and the homogenate is centrifuged to remove cell debris. The supernatant is then subjected to sequential ammonium sulfate precipitation. The fraction containing the substantially pure recombinant factor VIII is subjected to gel filtration in an appropriately sized dextran or polyacrylamide column to separate the recombinant factor VIII. If necessary, a protein fraction (containing the substantially pure recombinant factor VIII) may be further purified by high performance liquid chromatography (“HPLC”).

Another aspect of the present invention relates to an isolated nucleic acid molecule that encodes a recombinant mutant factor VIII as described herein. The isolated nucleic acid molecule encoding the recombinant mutant factor VIII can be an RNA or DNA. The nucleic acid codons can be further optimized for enhanced expression.

In one embodiment, the isolated nucleic acid molecule can have a nucleotide sequence encoding the amino acid sequence of SEQ ID NO:2 as modified with one of the substitutions at positions identified in this invention (i.e., possessing one to three nucleotide substitutions within codon 86 (nt256-258), codon 105 (nt:313-315), codon 108 (nt:322-324), codon 115 (nt:343-345), codon 117 (nt:349-351), codon 129 (nt:385-387), codon 132 (nt:394-396), codon 134 (nt:400-402), codon 147 (nt:439-441) and/or codon 152 (nt:454-456) of SEQ ID NO:1 (the first 57 nucleotides are not counted since they encode the signal peptides). The isolated nucleic acid molecule may have one or multiple changes in these positions in any combination.

In another embodiment, the isolated nucleic acid molecule can have a nucleotide sequence encoding a B-domainless factor VIII of the type described above, as modified with one or multiple substitutions at position(s) I86, Y105, A108, D115, Q117, F129, G132, H134, M147 and/or L152.

In another embodiment, the isolated nucleic acid molecule can have a nucleotide sequence encoding a chimeric human/porcine of the type described above, as modified with one or multiple substitutions at position(s) I86, Y105, A108, D115, Q117, F129, G132, H134, M147 and/or L152.

In a further embodiment, the isolated nucleic acid molecule can have a nucleotide sequence encoding a fused A2-A3 domain factor VIII of the type described above, as modified with one or multiple substitutions at position(s) I86, Y105, A108, D115, Q117, F129, G132, H134, M147 and/or L152.

In another embodiment, the isolated nucleic acid molecule can have a nucleotide sequence encoding a factor VIII whose inactivation sites have been modified as described above, as further modified with one or multiple substitutions at position(s) I86, Y105, A108, D115, Q117, F129, G132, H134, M147 and/or L152.

In yet another embodiment, the isolated nucleic acid molecule can have a nucleotide sequence encoding a factor VIII whose affinity for factor IXa and/or factor X has been enhanced, along with one or multiple substitutions at position(s) I86, Y105, A108, D115, Q117, F129, G132, H134, M147 and/or L152.

In a still further embodiment, the isolated nucleic acid molecule can have a nucleotide sequence encoding a factor VIII whose affinity for various serum-binding proteins has been altered to increase its circulating half-life and further modified with one or multiple substitutions at position(s) I86, Y105, A108, D115, Q117, F129, G132, H134, M147 and/or L152.

In a further embodiment, the isolated nucleic acid molecule can have a nucleotide sequence encoding a factor VIII that has increased secretion in culture, as further modified with one or multiple substitutions at position(s) I86, Y105, A108, D115, Q117, F129, G132, H134, M147 and/or L152.

In a further embodiment, the isolated nucleic acid molecule can have a nucleotide sequence encoding a factor VIII that possesses one or more non-naturally occurring glycosylation site(s) along with one or multiple substitutions at position(s) I86, Y105, A108, D115, Q117, F129, G132, H134, M147 and/or L152.

In yet another embodiment, the isolated nucleic acid molecule encodes a recombinant factor VIII that is modified with one or more substitutions at position(s) I86, Y105, A108, D115, Q117, F129, G132, H134, M147 and/or L152 and is further modified to possess any combination of the following modification: modified to be B-domainless, modified to be chimeric, modified to have fused A2-A3 domains, modified to have one or more altered inactivation cleavage site(s), modified to have enhanced factor IXa and/or factor X affinity, modified to have enhanced secretion, modified to have an increased circulating half-life, and modified to possess one or more non-naturally occurring glycosylation site(s).

Another aspect of the present invention relates to an expression vector for expressing the mutant factor VIII polynucleotides described herein. As used herein, the term “expression vector” refers to a viral or non-viral vector that comprise a polynucleotide encoding the novel peptide of the present invention in a form suitable for expression of the polynucleotide in a host cell. One type of non-viral vector is a “plasmid,” which includes a circular double-stranded DNA loop into which additional DNA segments can be ligated. In the present specification, “plasmid” and “vector” can be used interchangeably as the plasmid is the most commonly used form of vector.

When preparing an expression vector, the transgene sequences may be inserted into a plasmid containing suitable bacterial sequences for replication in bacterial, as well as eukaryotic cells. Any convenient plasmid may be employed, which can include markers allowing for selection in a bacterium, and generally one or more unique, conveniently located restriction sites. The selection of a vector will depend on the preferred transformation technique and target host for transformation.

Expression vectors for expressing mutant factor VIII polypeptides include one or more regulatory sequences operably linked to the polynucleotide sequence to be expressed. It will be appreciated by those skilled in the art that the design of the expression vector can depend on such factors as the choice of the host cell to be transformed, the level of expression of protein desired, and the like. The expression vectors of the invention can be introduced into host cells to thereby produce the mutant factor VIII proteins described herein.

As used herein, the term “control sequences” or “regulatory sequences” refers to DNA sequences necessary for the expression of an operably linked coding sequence in a particular host organism. The term “control/regulatory sequence” is intended to include promoters, enhancers and other expression control elements (e.g., polyadenylation signals). Control/regulatory sequences include those which direct constitutive expression of a nucleotide sequence in many types of host cells and those which direct expression of the nucleotide sequence only in certain host cells (e.g., tissue-specific regulatory sequences).

A nucleic acid sequence is “operably linked” to another nucleic acid sequence when the former is placed into a functional relationship with the latter. For example, a DNA for a presequence or secretory leader peptide is operably linked to DNA for a polypeptide if it is expressed as a preprotein that participates in the secretion of the polypeptide; a promoter or enhancer is operably linked to a coding sequence if it affects the transcription of the sequence; or a ribosome binding site is operably linked to a coding sequence if it is positioned so as to facilitate translation. Generally, “operably linked” means that the DNA sequences being linked are contiguous and, in the case of a secretory leader, contiguous and in reading phase. However, enhancers do not have to be contiguous. Linking is accomplished by ligation at convenient restriction sites. If such sites do not exist, synthetic oligonucleotide adaptors or linkers are used in accordance with conventional practice.

Suitable expression vectors for directing expression in mammalian cells generally include a promoter, as well as other transcription and translation control sequences known in the art. In certain embodiments, the mammalian expression vector is capable of directing expression of the polynucleotide preferentially in a particular cell type (e.g., tissue-specific regulatory elements are used to express the polynucleotide). Tissue-specific regulatory elements are known in the art and may include, for example, liver cell-specific promoters and/or enhancers (e.g., albumin promoter, α-1 antitrypsin promoter, apoE enhancer). Alternatively, a constitutive promoter (e.g., HCMV) active in virtually any cell type may be used.

In certain preferred embodiments, the expression vectors are viral vectors. Viral vectors typically have one or more viral genes removed and include a gene/promotor cassette inserted into a viral genome insertion site for insertion of exogenous transgenes, including the mutant factor VIII genes described herein. The necessary functions of the removed gene(s) may be supplied by cell lines which have been engineered to express the gene products of the early genes in trans. Exemplary viral vectors include, but are not limited to, adeno-associated viral (AAV) vectors, retroviral vectors, including lentiviral vectors, adenoviral vectors, herpes viral vectors, and alphavirus vectors. Other viral vectors include astrovirus, coronavirus, orthomyxovirus, papovavirus, paramyxovirus, parvovirus, picornavirus, poxvirus, togavirus viral vectors and the like. The viral vector may comprise any suitable nucleic acid construct, such as a DNA or RNA construct and may be single stranded, double stranded, or duplexed.

Once the DNA construct of the present invention has been prepared, it is ready to be incorporated into a host cell. Accordingly, another aspect of the present invention relates to a method of making a recombinant cell comprising a factor VIII nucleic acid. Basically, this entails introducing the DNA construct into cells via transformation, transduction, electroporation, calcium phosphate precipitation, liposomes and the like and selecting for cells that have incorporated the DNA episomally or integrated into the host genome.

Thus, a further aspect of the present invention relates to a host cell including an isolated nucleic acid molecule encoding the recombinant factor VIII of the present invention. The host cell can contain the isolated nucleic acid molecule as a DNA molecule in the form of an episomal plasmid or stably integrated into the host cell genome. Further, the host cell can constitute an expression system for producing the recombinant mutant factor VIII protein. Suitable host cells can be, without limitation, animal cells (e.g., baby hamster kidney (“BHK”) cells), Chinese hamster ovary cells (“CHO”), bacterial cells (e.g., E. coli), insect cells (e.g., Sf9 cells), fungal cells, yeast cells (e.g., Saccharomyces or Schizosaccharomyces), plant cells (e.g., Arabidopsis or tobacco cells), algal cells and the like.

Another aspect of the present invention relates to a method of making a recombinant factor VIII of the present invention. This method involves growing a host cell of the present invention under conditions whereby the host cell expresses the recombinant factor VIII. The recombinant factor VIII is then isolated. In one embodiment, the host cell is grown in vitro in a growth medium. In a particular embodiment, suitable growth media can include, without limitation, a growth medium containing a von Willebrand Factor (referred to herein as “VWF”). In this embodiment, the host cell can contain a transgene encoding a VWF or the VWF can be introduced to the growth medium as a supplement. VWF in the growth medium will allow for greater expression levels of the recombinant factor VIII. Once the recombinant factor VIII is secreted into the growth medium, it can then be isolated from the growth medium using techniques well-known by those of ordinary skill in the relevant recombinant DNA and protein arts (including those described herein). In another embodiment, the method of making the recombinant factor VIII of the present invention further involves disrupting the host cell prior to isolation of the recombinant factor VIII. In this embodiment, the recombinant factor VIII is isolated from cellular debris.

When recombinantly produced, the factor VIII protein or polypeptide (or fragment or mutant thereof) is expressed in a recombinant host cell, typically, although not exclusively, a eukaryote. In certain preferred embodiments, eukaryotic host cells, such as mammalian cells, are used to produce mutant factor VIII polypeptides as described herein. Mammalian cells suitable for carrying out the present invention include, among others: COS (e.g., ATCC No. CRL 1650 or 1651), BHK (e.g., ATCC No. CRL 6281), CHO (ATCC No. CCL 61), HeLa (e.g., ATCC No. CCL 2), 293 (ATCC No. 1573), CHOP, and NS-1 cells.

Another aspect of the present invention relates to a method for treating patient with a factor VIII deficiency. In one embodiment, this involves administering to a patient in need thereof a recombinant mutant factor VIII (as described herein) in an amount effective for treating the factor VIII deficiency.

In a particular embodiment, the recombinant factor VIII, alone, or in the form of a pharmaceutical composition (i.e., in combination with stabilizers, delivery vehicles, and/or carriers) is infused into patients intravenously according to the same procedure that is used for infusion of human or animal factor VIII. A suitable effective amount of the recombinant factor VIII can include, without limitation, between about 10 to about 500 units/kg body weight of the patient.

In another embodiment, a method for treating patient with a factor VIII deficiency comprises administering to a patient in need thereof a pharmaceutical composition comprising an expression vector encoding a mutant factor VIII, or a functional fragments thereof, in an amount effective for treating the factor VIII deficiency. In certain embodiments, the recombinant factor VIII can be administered by transplanting cells genetically engineered to produce the recombinant factor VIII, typically via implantation of a device containing such cells. Such transplantation typically involves using recombinant dermal fibroblasts, a non-viral approach (Roth, et al., New Engl. J. Med. 344:1735-1742 (2001)).

Administration of FVIII-encoding expression vectors to factor VIII deficient patients can result in sufficient expression of FVIII polypeptide to functionally reconstitute the coagulation cascade. The expression vector(s) may be administered alone or in combination with other therapeutic agents in a pharmaceutically acceptable or biologically compatible composition.

The FVIII-encoding polynucleotide can be employed as a single chain molecule containing both heavy and light chain portions (FIG. 10) or split into two or multiple molecules (e.g., heavy and light chain; FIG. 11) in viral or non-viral vectors for delivery into host cells of the patient.

In a preferred embodiment of the invention, the expression vector comprising nucleic acid sequences encoding the mutant FVIII mutants is a viral vector. Viral vectors which may be used in the present invention include, but are not limited to, adenoviral vectors (with or without tissue specific promoters/enhancers), adeno-associated virus (AAV) vectors of multiple serotypes (e.g., AAV-1 to AAV-12, and others) and hybrid AAV vectors, lentivirus vectors and pseudo-typed lentivirus vectors [e.g., Ebola virus, vesicular stomatitis virus (VSV), and feline immunodeficiency virus (FIV)], herpes simplex virus vectors, vaccinia virus vectors, retroviral vectors, lentiviral vectors, non-viral vectors and others.

In certain preferred embodiments, methods are provided for the administration of a viral vector comprising nucleic acid sequences encoding a mutant FVIII, or a functional fragment thereof involve the use of AAV vectors or lentiviral vectors. Most preferably, only the essential parts of vector e.g., the ITR and LTR elements, respectively are included. Direct delivery of vectors or ex-vivo transduction of human cells and followed by infusion into the body will result in expression of mutant FVIIIs thereby exerting a beneficial therapeutic effect on hemostasis by enhancing pro-coagulation activity.

Recombinant AAV and lentiviral vectors have found broad utility for a variety of gene therapy applications. Their utility for such applications is due largely to the high efficiency of in vivo gene transfer achieved in a variety of organ contexts. AAV and lentiviral particles may be used to advantage as vehicles for effective gene delivery. Such virions possess a number of desirable features for such applications, including tropism for dividing and non-dividing cells. Early clinical experience with these vectors also demonstrated no sustained toxicity and immune responses were minimal or undetectable. AAV are known to infect a wide variety of cell types in vivo and in vitro by receptor-mediated endocytosis or by transcytosis. These vector systems have been tested in humans targeting retinal epithelium, liver, skeletal muscle, airways, brain, joints and hematopoietic stem cells. It is likely that non-viral vectors based on plasmid DNA or minicircles will be also suitable gene transfer vectors for a large gene as that encoding FVIII.

It is desirable to introduce a vector that can provide, for example, sufficient expression of a desired gene and minimal immunogenicity. Improved AAV and lentiviral vectors and methods for producing such vectors have been described in detail in a number of references, patents, and patent applications, including Wright J. F. (Hum Gene Ther 20:698-706, 2009) which describes the production of clinical grade vectors. Lentiviral vector can be produced at CHOP and the other vectors are available through the Lentivirus vector production core laboratory by NHLBI Gene Therapy Resource Program (GTRP)-Lentivirus Vector Production Core Laboratory.

For some applications, an expression construct may further comprise regulatory elements which serve to drive expression in a particular cell or tissue type. Such regulatory elements are known to those of skill in the art and discussed in depth in Sambrook, et al. (1989) and Ausubel, et al. (1992). The incorporation of tissue specific regulatory elements in the expression constructs of the present invention provides for at least partial tissue tropism for the expression of the mutant FVIIIs or functional fragments thereof. For example, nucleic acid sequences encoding mutant FVIII under the control of a cytomegalovirus (CMV) promoter can be employed for skeletal muscle expression or the hAAT-ApoE and others for liver specific expression. Hematopoietic specific promoters in lentiviral vectors may also be used to advantage in the methods of the present invention.

In a preferred embodiment, the mutant FVIII sequence is provided as a component of a viral vector packaged in a capsid. In a particularly preferred embodiment, an AAV vector is used for in vivo delivery of the mutant FVIIIs (Gnatenko, et al., Br. J. Haematol. 104:27-36 (1999)). In this case, the AAV vector includes at least one mutant FVIII and associated expression control sequences for controlling expression of the mutant FVIII sequence. As shown in FIGS. 10 and 11, exemplary AAV vectors for expressing mutant FVIII sequences may include promoter-enhancer regulatory regions for FVIII expression and cis-acting ITRs functioning to enable promote replication and packaging of the mutant FVIII nucleic acids into AAV capsids and integration of the mutant FVIII nucleic acid into the genome of a target cell. Preferably, the AAV vector has its rep and cap genes deleted and replaced by the mutant hFVIII sequence and its associated expression control sequences. As shown in FIGS. 10 and 11, the mutant FVIII sequence is typically inserted adjacent to one or two (i.e., flanked by) AAV TRs or TR elements adequate for viral replication. Other regulatory sequences suitable for facilitating tissue-specific expression of the mutant hFVIII sequence in the target cell may also be included.

The viral capsid component of the packaged viral vectors may be a parvovirus capsid. AAV Cap and chimeric capsids are preferred. Examples of suitable parvovirus viral capsid components are capsid components from the Parvoviridae family, such as an autonomous parvovirus or a dependovirus. For example, the viral capsid may be an AAV capsid (e.g., AAV1, AAV2, AAV3, AAV4, AAV5, AAV6, AAV7, AAV8, AAV9, AAV10, AAV11 or AAV12 capsid; one skilled in the art would know there are likely other variants not yet identified that perform the same or similar function), or may include components from two or more AAV capsids. A full complement of AAV Cap proteins includes VP1, VP2, and VP3. The ORF comprising nucleotide sequences encoding AAV VP capsid proteins may comprise less than a full complement AAV Cap proteins or the full complement of AAV Cap proteins may be provided.

One or more of the AAV Cap proteins may be a chimeric protein, including amino acid sequences AAV Caps from two or more viruses, preferably two or more AAVs, as described in Rabinowitz et al., U.S. Pat. No. 6,491,907. For example, the chimeric virus capsid can include an AAV1 Cap protein or subunit and at least one AAV2 Cap or subunit. The chimeric capsid can, for example, include an AAV capsid with one or more B19 Cap subunits, e.g., an AAV Cap protein or subunit can be replaced by a B19 Cap protein or subunit. For example, the Vp3 subunit of the AAV capsid can be replaced by the Vp2 subunit of B19.

Packaging cells may be cultured to produce packaged viral vectors of the invention. The packaging cells may include heterologous (1) viral vector function(s), (2) packaging function(s), and (3) helper function(s). The viral vector functions typically include a portion of a parvovirus genome, such as an AAV genome, with rep and cap deleted and replaced by the mutant FVIII sequence and its associated expression control sequences as described above.

In certain embodiments, the viral vector functions may suitably be provided as duplexed vector templates, as described in U.S. Patent Publication No. 2004/0029106 to Samulski et al. Duplexed vectors are dimeric self-complementary (sc) polynucleotides (typically, DNA). For example, the DNA of the duplexed vectors can be selected so as to form a double-stranded hairpin structure due to intrastrand base pairing. Both strands of the duplexed DNA vectors may be packaged within a viral capsid. The duplexed vector provides a function comparable to double-stranded DNA virus vectors and can alleviate the need of the target cell to synthesize complementary DNA to the single-stranded genome normally encapsidated by the virus.

The TR(s) (resolvable and non-resolvable) selected for use in the viral vectors are preferably AAV sequences (from any AAV serotype). Resolvable AAV ITRs need not have a wild-type TR sequence (e.g., a wild-type sequence may be altered by insertion, deletion, truncation or missense mutations), as long as the TR mediates the desired functions, e.g., virus packaging, integration, and/or provirus rescue, and the like. The TRs may be synthetic sequences that function as AAV inverted terminal repeats, such as the “double-D sequence” as described in U.S. Pat. No. 5,478,745 to Samulski et al. Typically, but not necessarily, the TRs are from the same parvovirus, e.g., both TR sequences are from AAV2.

The packaging functions include capsid components. The capsid components are preferably from a parvoviral capsid, such as an AAV capsid or a chimeric AAV capsid function. Examples of suitable parvovirus viral capsid components are capsid components from the family Parvoviridae, such as an autonomous parvovirus or a Dependovirus. For example, the capsid components may be selected from AAV capsids, e.g., AAV1-AAV12 and other novel capsids as yet unidentified or from non-human primate sources. Capsid components may include components from two or more AAV capsids.

In certain embodiments, one or more of the VP capsid proteins may comprise chimeric proteins, comprising amino acid sequences from two or more viruses, preferably two or more AAVs, as described in Rabinowitz et al., U.S. Pat. No. 6,491,907. For example, the chimeric virus capsid can include a capsid region from an adeno-associated virus (AAV) and at least one capsid region from a B19 virus. The chimeric capsid can, for example, include an AAV capsid with one or more B19 capsid subunits, e.g., an AAV capsid subunit can be replaced by a B19 capsid subunit. For example, the VP1, VP2 or VP3 subunit of the AAV capsid can be replaced by the VP1, VP2 or VP3 subunit of B19. As another example, the chimeric capsid may include an AAV type 2 capsid in which the type 2 VP1 subunit has been replaced by the VP1 subunit from an AAV type 1, 3, 4, 5, or 6 capsid, preferably a type 3, 4, or 5 capsid. Alternatively, the chimeric parvovirus has an AAV type 2 capsid in which the type 2 VP2 subunit has been replaced by the VP2 subunit from an AAV type 1, 3, 4, 5, or 6 capsid, preferably a type 3, 4, or 5 capsid. Likewise, chimeric parvoviruses in which the VP3 subunit from an AAV type 1, 3, 4, 5 or 6 (more preferably, type 3, 4 or 5) is substituted for the VP3 subunit of an AAV type 2 capsid are preferred. As a further alternative, chimeric parvoviruses in which two of the AAV type 2 subunits are replaced by the subunits from an AAV of a different serotype (e.g., AAV type 1, 3, 4, 5 or 6) are preferred. In exemplary chimeric parvoviruses according to this embodiment, the VP1 and VP2, or VP1 and VP3, or VP2 and VP3 subunits of an AAV type 2 capsid are replaced by the corresponding subunits of an AAV of a different serotype (e.g., AAV type 1, 3, 4, 5 or 6). Likewise, in other preferred embodiments, the chimeric parvovirus has an AAV type 1, 3, 4, 5 or 6 capsid (preferably the type 2, 3 or 5 capsid) in which one or two subunits have been replaced with those from an AAV of a different serotype, as described above for AAV type 2.

The packaged viral vector generally includes the mutant FVIII sequence and expression control sequences flanked by TR elements sufficient to result in packaging of the vector DNA and subsequent expression of the mutant FVIII sequence in the transduced cell. The viral vector functions may, for example, be supplied to the cell as a component of a plasmid or an amplicon. The viral vector functions may exist extrachromosomally within the cell line and/or may be integrated into the cells' chromosomal DNA.

In a preferred embodiment, the mutant FVIII described herein are used for gene therapy of FVIII associated disorders, such as hemophilia A. In this case, expression of the mutant FVIII transgene can enhance clotting in a subject otherwise vulnerable to uncontrolled bleeding due to factor VIII deficiency (e.g., intraarticular, intracranial, or gastrointestinal hemorrhage), including hemophiliacs who have developed antibodies to human factor VIII. The target cells of the vectors are cells capable of expressing polypeptides with FVIII activity, such as those of the hepatic system of a mammal, endothelial cells and other cells with the proper cellular machinery to process the precursor to yield protein with FVIII activity.

In particular embodiments, the present invention provides a pharmaceutical composition comprising a vector of the present invention including a modified gene of FVIII in a pharmaceutically-acceptable carrier and/or other medicinal agents, pharmaceutical agents, carriers, adjuvants, diluents, etc.

The treatment dosages of recombinant factor VIII that should be administered to a patient in need of such treatment will vary depending on the severity of the factor VIII deficiency. Generally, dosage level is adjusted in frequency, duration, and units in keeping with the severity and duration of each patient's bleeding episode. Accordingly, the recombinant factor VIII is included in a pharmaceutically acceptable carrier, delivery vehicle, or stabilizer in an amount sufficient to deliver to a patient a therapeutically effective amount of the protein to stop bleeding, as measured by standard clotting assays.

Factor VIII is classically defined as that substance present in normal blood plasma that corrects the clotting defect in plasma derived from individuals with hemophilia A. The coagulant activity in vitro of purified and partially-purified forms of factor VIII is used to calculate the dose of recombinant factor VIII for infusions in human patients and is a reliable indicator of activity recovered from patient plasma and of correction of the in vivo bleeding defect. There are no reported discrepancies between standard assay of novel factor VIII molecules in vitro and their behavior in the dog infusion model or in human patients, according to Lusher, et al., New Engl. J. Med. 328:453-459 (1993); Pittman, et al., Blood 79:389-397 (1992); and Brinkhous, et al., Proc. Natl. Acad. Sci. 82:8752-8755 (1985).

Usually, the desired plasma factor VIII activity level to be achieved in the patient through administration of the recombinant factor VIII is in the range of 30-200% of normal. In one embodiment, administration of the therapeutic recombinant factor VIII is given intravenously at a preferred dosage in the range from about 5 to 500 units/kg body weight, and particularly in a range of 10-100 units/kg body weight, and further particularly at a dosage of 20-40 units/kg body weight; the interval frequency is in the range from about 8 to 24 hours (in severely affected hemophiliacs); and the duration of treatment in days is in the range from 1 to 10 days or until the bleeding episode is resolved. See, e.g., Roberts, H. R., and M. R. Jones, “Hemophilia and Related Conditions—Congenital Deficiencies of Prothrombin (Factor II, Factor V, and Factors VII to XII),” Ch. 153, 1453-1474, 1460, in Hematology, Williams, W. J., et al., ed. (1990). Patients with inhibitors may require a different amount of recombinant factor VIII than their previous form of factor VIII. For example, patients may require less recombinant factor VIII because of its higher specific activity than the wild-type VIII and its decreased antibody reactivity. As in treatment with human or plasma-derived factor VIII, the amount of therapeutic recombinant factor VIII infused is defined by the one-stage factor VIII coagulation assay and, in selected instances, in vivo recovery is determined by measuring the factor VIII in the patient's plasma after infusion. It is to be understood that for any particular subject, specific dosage regimens should be adjusted over time according to the individual need and the professional judgment of the person administering or supervising the administration of the compositions, and that the concentration ranges set forth herein are exemplary only and are not intended to limit the scope or practice of the claimed recombinant factor VIII.

Treatment can take the form of a single intravenous administration of the recombinant factor VIII or periodic or continuous administration over an extended period of time, as required. Alternatively, therapeutic recombinant factor VIII can be administered subcutaneously or orally with liposomes in one or several doses at varying intervals of time

For injection, the carrier will typically be a liquid. For other methods of administration, the carrier may be either solid or liquid. For inhalation administration, the carrier will be respirable, and will preferably be in solid or liquid particulate form. As an injection medium, it is preferred to use water that contains the additives usual for injection solutions, such as stabilizing agents, salts or saline, and/or buffers.

Exemplary pharmaceutically acceptable carriers include sterile, pyrogen-free water and sterile, pyrogen-free, phosphate buffered saline. Physiologically-acceptable carriers include pharmaceutically-acceptable carriers. Pharmaceutically acceptable carriers are those which are that is not biologically or otherwise undesirable, i.e., the material may be administered to a subject without causing undesirable biological effects which outweigh the advantageous biological effects of the material. A pharmaceutical composition may be used, for example, in transfection of a cell ex vivo or in administering a viral vector or cell directly to a subject.

Recombinant virus vectors comprising the modified gene of FVIII are preferably administered to the cell in a biologically-effective amount. If the virus vector is administered to a cell in vivo (e.g., the virus is administered to a subject as described below), a biologically-effective amount of the virus vector is an amount that is sufficient to result in transduction and expression of the transgene in a target cell.

The cells transduced with a viral vector are preferably administered to the subject in a “therapeutically-effective amount” in combination with a pharmaceutical carrier. Those skilled in the art will appreciate that the therapeutic effects need not be complete or curative, as long as some benefit is provided to the subject.

Dosages of the cells to administer to a subject will vary upon the age, condition and species of the subject, the type of cell, the nucleic acid being expressed by the cell, the mode of administration, and the like. Typically, at least about 10² to about 10⁸, preferably about 10³ to about 10⁸ cells, will be administered per dose. Preferably, the cells will be administered in a therapeutically-effective amount.

Administration of the vector to a human subject or an animal in need thereof can be by any means known in the art for administering virus vectors. Exemplary modes of administration include rectal, transmucosal, topical, transdermal, inhalation, parenteral (e.g., intravenous, subcutaneous, intradermal, intramuscular, and intraarticular) administration, and the like, as well as direct tissue or organ injection, alternatively, intrathecal, direct intramuscular, intraventricular, intravenous, intraperitoneal, intranasal, or intraocular injections. Injectables can be prepared in conventional forms, either as liquid solutions or suspensions, solid forms suitable for solution or suspension in liquid prior to injection, or as emulsions. Alternatively, one may administer the virus in a local rather than systemic manner, for example, in a depot or sustained-release formulation.

In other preferred embodiments, the inventive vector comprising the mutant FVIII gene is administered intramuscularly, more preferably by intramuscular injection or by local administration. The vectors disclosed herein may be administered to the lungs of a subject by any suitable means, but are preferably administered by administering an aerosol suspension of respirable particles comprised of the inventive parvovirus vectors, which the subject inhales. The respirable particles may be liquid or solid. Aerosols of liquid particles comprising the inventive parvovirus vectors may be produced by any suitable means, such as with a pressure-driven aerosol nebulizer or an ultrasonic nebulizer, as is known to those of skill in the art. See, e.g., U.S. Pat. No. 4,501,729.

Dosages of the virus vector with the mutant FVIII gene will depend upon the mode of administration, the disease or condition to be treated, the individual subject's condition, the particular viral vector, and the gene to be delivered, and can be determined in a routine manner. Exemplary doses for achieving therapeutic effects are virus titers of at least about 10⁵, 10⁶, 10⁷, 10⁸, 10⁹, 10¹⁰, 10¹¹, 10¹², 10¹³, 10¹⁴, 10¹⁵ transducing units or more, preferably about 10⁸-10¹³ transducing units, yet more preferably 10¹² transducing units. The mutant FVIII genes may be administered as components of a DNA molecule having regulatory elements appropriate for expression in the target cells. The mutant FVIII genes may be administered as components of viral plasmids, such as rAAV vectors. Viral particles may be administered as viral particles alone, whether as an in vivo direct delivery to the portal vasculature or as an ex vivo treatment comprising administering the vector viral particles in vitro to cells from the animal receiving treatment followed by introduction of the transduced cells back into the donor.

The present invention is further illustrated by the following examples which should not be construed as limiting. The contents of all references, patents, and published patent applications cited throughout this application are incorporated herein by reference.

EXAMPLE 1 Construction, Expression and Purification of B-Domainless Factor VIII Mutants

Plasmid pAAV-CB-F8 carries a B-domainless human factor VIII (hF8) cDNA under the control of a CB promoter (beta-actin promoter with a CMV enhancer). This plasmid, consistent with the construction shown in FIG. 10, was used as template for making various hF8 mutants. A hF8 cDNA fragment encoding the substitution mutations I86V, Y105F, A108S, D115E, Q117H, F129L, G132K, H134Q, M147T and L152P was synthesized chemically and used to replace the corresponding region of pAAV-CB-F8. The resulting plasmid (pAAV-CB-F8-X10) expresses a mutant factor VIII protein with the above 10 mutations (F8-X10; SEQ ID NO: 3).

A factor VIII cDNA fragment encoding the substitution mutations I86V, A108S, G132K, M147T, L152P was synthesized chemically and used to replace the corresponding region of pAAV-CB-F8. The resulting plasmid (pAAV-CB-F8-X5) expresses a mutant factor VIII protein with the above 5 mutations (F8-X5; SEQ ID NO:4).

Site-directed mutagenesis was used to introduce individual mutations corresponding to I86, Y105, A108, D115, Q117, F129, G132, H134, M147, L152 of human factor VIII in the pAAV-CB-F8 plasmid. The resulting plasmids include pAAV-CB-F8-I86V, pAAV-CB-F8-Y105F, pAAV-CB-F8-A1 08S, pAAV-CB-F8-D115E, _(p)AAV-CB-F8-Q117H, pAAV-CB-F8-F129L, pAAV-CB-F8-G132K, pAAV-CB-F8-H134Q and pAAV-CB-F8-M147T, pAAV-CB-F8-L152P.

Site-directed mutagenesis was also used to revert back individual mutations in amino acids 86, 105, 108, 115, 117, 129, 132, 134, 147, 152 of hF8-X10 in the pAAV-CB-F8-X10 plasmid to wild-type human amino acids. The resulting plasmids include pAAV-CB-F8-X10-V86I, pAAV-CB-F8-X10-F105Y, pAAV-CB-F8-X10-5108A, _(p)AAV-CB-F8-X10-E115D, pAAV-CB-F8-X10-H117Q, pAAV-CB-F8-X10-L129F, _(p)AAV-CB-F8-X10-K132G, pAAV-CB-F8-X10-Q134H, pAAV-CB-F8-X10-T147M, _(p)AAV-CB-F8-X10-P152L. These mutants were tested as described Example 4 (FIG. 7) below.

A set of degenerated oligonucleotides with NNN corresponding to G132 position was used to create all 19 mutations corresponding to G132. The resulting factor VIII mutant plasmids include pAAV-CB-F8-G132A, pAAV-CB-F8-G132I, . . . pAAV-CB-F8-G132V etc. The last letter indicates the amino acid substitution at that particular position. A similar strategy can be used to generate other substitutions in accordance with the present invention.

The above described plasmids contain an AAV-ITR and can be used to generate AAV vectors. A liver specific promoter can be used to replace the CB promoter to reduce the size of the expression cassette and to improve vector packaging and expression in the liver. Other tissue specific promoter can also be used as well.

Sequences between the FVIII heavy chain and the FVIII stop codon were removed from the FVIII expression vectors. The resulting heavy chain (HC) mutants contain the first 745 amino acid of FVIII and lack B domain (BDD) and light chain (LC) sequences. The plasmid pAAV-CB-HC-X10 contains mutations corresponding to I86V, Y105F, A108S, D115E, Q117H, F129L, G132K, H134Q, M147T and L152P in the heavy chain. The plasmid pAAV-CB-HC-X5 contains mutations corresponding to I86V, A108S, G132K, M147T, L152P in the heavy chain. The plasmid pAAV-CB-HC-G132K contains the G132K mutation in the heavy chain. Alternatively, acidic region 3 (a3) can be added to these constructs to obtain HC mutants in an HC1690 background.

EXAMPLE 2 Comparison of Different Factor VIII Mutants for Secretion in Tissue Culture Cells

Plasmids pAAV-CB-hBDD-F8 (wt), pAAV-CB-hBDD-F8-X10, pAAV-CB-hBDD-F8-X5 and pAAV-CB-hBDD-F8-G312K were separately transfected in BHK cells (panel A) or 293 cells (panel B). Secreted F8 in the media was harvested and assayed by aPTT assay at 48 hours post transfection. The expression/secretion by wild type human BDD-F8(hBDD) was set as 100%. As shown in FIG. 7, the hF8 mutants were secreted at about 2-8.5 fold higher expression levels than the wild type hF8.

EXAMPLE 3 Comparison of Human Factor VIII Mutant Secretion In Vivo

Plasmids pAAV-CB-hBDDF8 (B-domain deleted (BDD) wt hF8), pAAV-CB-hBDDF8-X10 (hF8-BDD with 10 substitutions; SEQ ID NO:3), pAAV-CB-hBDD-F8-X5(hF8 with 5 substitutions; SEQ ID NO:4) and pAAV-CB-hBDD-F8-G312K (hF8 with G132K substitution) were separately injected to Blab/c and F8 double knock-out mice. Secreted F8 in the blood was collected and assayed by aPTT assay at 48 hours post injection. The expression/secretion by wild type human F8 (hBDD-F8) was set as 100%. All mutants described here outperform the wild type factor VIII. As shown in FIG. 8, the hF8 mutants were secreted at about 1.2-5.2 fold higher expression levels than the wild type hF8.

EXAMPLE 4 Comparison of Different Factor VIII Mutants in Secretion

Plasmids encoding amino acids in hBDD-F8-X10 were modified to revert back the mutant substitutions to their corresponding wild type amino acids as indicated in the table. For example, hBDD-F8-X10-V86I means that “V86” in hBDD-F8-X10 was changed back to “I”. In hBDD-F8-X10-6p, 6 of 10 mutant amino acids in hBDD-F8-X10 were reverted back to their corresponding wild type amino acids. The above plasmids were separately transfected in 293 cells. Secreted F8 in the media was harvested and assayed by aPTT assay at 48 hours post transfection. The expression/secretion by hBDD-F8-X10 was set as 100%. As shown in FIG. 9, all of the revertants exhibited reduced expression and secretion as compared to the hBDD-F8-X10 mutant.

EXAMPLE 4 Comparison of Different Factor VIII Mutants in Secretion

AAV8 vector AAV-apoEhAAT-hF8HC1690 (carrying human factor VIII heavy chain aa#1-745 and a3 sequence, apoEhAAT: human alpha one antitrypsin promoter with apo E enhancer) and AAV-apoEhAAT-hF8-HC-X10 (hF8HC with 10 substitutions) were each separately injected in F8 knock-out mice with a light chain expression vector (dose: each vector 1E11 particles/mouse). Secreted F8 in the blood was collected and assayed by aPTT assay the indicated times. The expression/secretion by wild type human F8 heavy chain (hF8-HC1690) was set as 100%. The hF8-HC1690-X10 mutant described here outperform the wild type heavy chain expression. As shown in FIG. 10, the hF8-HC1690-X10 mutant was secreted at about 6-20 fold higher expression levels compared to wild type hF8HC.

EXAMPLE 6 Comparison of G132 Factor VIII Heavy Chain Mutants in Secretion in 293 Cells

Plasmid pAAV-CB-hF8-HC1690 (carrying human factor VIII heavy chain aa#1-745 and a3 sequence; see FIG. 1) or plasmids with indicated substitutions at G132 were transfected in 293 cells with an F8 light chain (LC) expression plasmid. Secreted F8 in the media was collected and assayed by aPTT assay at 48 hours post transfection. The expression/secretion by wild type human F8 heavy chain (hF8-HC1690) was set as 100%. As shown in FIG. 11, the F8 G132HC1690 mutants were secreted at about 1.4-3.4 fold higher expression levels compared to wild type hF8HC.

EXAMPLE 7 Comparison of Different Factor VIII Heavy Chain Mutants in Expression/Secretion In Vivo

Plasmids pAAV-CB-hF8-HC1690 (carrying human factor VIII heavy chain aa#1-745 and acidic region 3 (a3) sequence; see FIGS. 1, 6), pAAV-CB-hF8-HC1690-X10 (hF8 heavy chain with 10 substitutions; SEQ ID NO:5), pAAV-CB-hF8-HC1690-X5 (hF8 heavy chain with 5 substitutions along with a3 sequence; SEQ ID NO:6) and pAAV-CB-hF8-HC1690-G312K (hF8 heavy chain with G132K substitution and a3 sequence) were separately injected in Blab/c and F8 double knock-out mice along with a light chain expression plasmid. Secreted F8 in the blood was collected and assayed by aPTT assay at 48 hours post injection. The expression/secretion by wild type human F8 heavy chain (hF8-HC1690) was set as 100%. As shown in FIG. 12, the hF8 mutants were secreted at about 2.5-4.5 fold higher expression levels than the wild type hF8HC.

EXAMPLE 8 Comparison of L152 Factor VIII Heavy Chain Mutants in Secretion in 293 Cells

Plasmid pAAV-CB-hF8-HC1690 (carrying human factor VIII heavy chain aa#1-745 and a3 sequence; see FIGS. 1, 6) or plasmids with indicated substitutions at L152 were separately transfected in 293 cells with a hF8 light chain expression plasmid. Secreted hF8 in the media was collected and assayed by aPTT assay at 48 hours post transfection. The expression/secretion by wild type human F8 heavy chain (hF8-HC1690) was set as 100%. The hF8-L152HC mutants are identified by their specific amino acid substitutions in the Figure. As shown in FIG. 13, the hF8-L152HC mutants were secreted at about 1.4-3.5 fold higher expression levels compared to wild type hF8HC.

EXAMPLE 9 Comparison of A108 Factor VIII Heavy Chain Mutants in Secretion in 293 Cells

Plasmid pAAV-CB-hF8-HC1690 (carrying human factor VIII heavy chain aa#1-745 and a3 sequence; see FIG. 1) or plasmids with indicated substitutions at A108 were separately transfected in 293 cells with a hF8 light chain expression plasmid. Secreted hF8 in the media was collected and assayed by aPTT assay at 48 hours post transfection. The hF8-A108HC mutants are identified by their specific amino acid substitutions in the Figure. The expression/secretion by wild type human F8 heavy chain (hF8-HC1690) was set as 100%. As shown in FIG. 14, the majority of hF8-A108HC mutants were secreted at higher expression levels compared to wild type hF8HC.

EXAMPLE 10 Comparison of M147 Factor VIII Heavy Chain Mutants in Secretion in 293 Cells

Plasmid pAAV-CB-hF8-HC1690 (carrying human factor VIII heavy chain aa#1-745 and a3 sequence; see FIG. 1) or plasmids with indicated substitutions at M147 were separately transfected in 293 cells with a hF8 light chain expression plasmid. Secreted hF8 in the media was collected and assayed by hF8 ELISA at 48 hours post transfection. The hF8-M147HC mutants are identified by their specific amino acid substitutions in the Figure. The expression/secretion by wild type human F8 heavy chain (hF8-HC1690) was set as 100%. As shown in FIG. 15, the majority of hF8-M147HC mutants were secreted at higher expression levels compared to wild type hF8HC.

EXAMPLE 11 Neutralizing Antibodies Against 5 Mutated Amino Acids Were not Detected in the F8−/− Rat Model

F8−/− rats in a WAG/RijYcb background with single mutation in the A1 domain (Leu176Pro) were administered AAV-TTR-hF8-X10 at 1×10¹² viral particles/per rat. Of 3 injected rats, two were confirmed to develop rat anti-human factor VIII inhibitory antibodies against factor VIII as determined by a Bethesda assay. Panel A is representative of inhibitor levels in rat plasma at week 8. Panel B shows the activity of F8 remains in the supernatant after antibody absorption. To determine whether the inhibitory antibodies specifically target the 5 mutated amino acids, we used an excess of biotinylated recombinant human F8 (1.2 μg of Bio-F8) to saturate the inhibitory antibodies against regular FVIII in rat plasma. Then 30 μl of streptavidin agarose was used to pull down antigen-antibody complexes by rotation at room temperature for 1 hour and then centrifuged at 10,000 rpm for 2 min. An equivalent amount of biotinylated BSA (Bio-BSA) was used as a control. 200 ng of BDD-F8-X5 concentrate from a stably expressing cell line was then added to the rat plasma pretreated with Bio-F8 or Bio-BSA. Rat plasma without pretreatment was used as control. The F8 activity in the supernatant was determined by one-stage aPTT assay. As shown in FIG. 15, neutralizing antibodies against the five mutated amino acids were not detected in this F8−/− rat model.

The above Examples show that the mutant factor VIII products of the present invention express and/or secrete better than wild type factor VIII, therefore they can decrease the production cost and improve transgene expression levels when using a gene transfer vector. They can also allow lower vector doses to be administered and higher factor VIII expression levels.

The above description is for the purpose of teaching a person of ordinary skill in the art how to practice the present invention. It is not intended to detail all those obvious modifications and variations of it which will become apparent to the skilled worker upon reading the description. It is intended, however, that all such obvious modifications and variations be included within the scope of the present invention, which is defined by the following claims. The claims are intended to cover the claimed components and steps in any sequence effective to meet the objectives there intended, unless the context specifically indicates the contrary. 

What is claimed is:
 1. An isolated human factor VIII polypeptide mutant comprising one or more amino acid substitution(s) selected from the group consisting of I86, Y105, A108, D115, Q117, F129, G132, H134, M147 and L152.
 2. The mutant of claim 1, wherein the one or more amino acid substitution(s) are selected from the group consisting I86V, Y105F, A108S, D115E, Q117H, F129L, G132K, H134Q, M147T and L152P.
 3. The mutant of claim 1, comprising amino acid substitutions in each of amino acids I86, Y105, A108, D115, Q117, F129, G132, H134, M147 and L152.
 4. The mutant of claim 3, comprising each of the amino acid substitutions I86V, Y105F, A108S, D115E, Q117H, F129L, G132K, H134Q, M147T and L152P
 5. The mutant of claim 1, wherein the one or more amino acid substitution(s) are selected from the group consisting of I86, A108, G132, M147 and L152P.
 6. The mutant of claim 5, wherein the one or more amino acid substitution(s) are selected from the group consisting of I86V, A108S, G132K, M147T and L152P.
 7. The mutant of claim 5, comprising amino acid substitutions in each of amino acids I86, A108, G132, M147 and L152.
 8. The mutant of claim 7, comprising amino acid substitutions in each of amino acids I86V, A108S, G132K, M147T and L152P.
 9. The mutant of any one of claims 1 to 8, further comprising a deletion in the B domain of human factor VIII.
 10. The mutant of claim 9, further comprising the a2 and/or a3 domain(s) of human factor VIII.
 11. An isolated polynucleotide encoding the mutant of any one of claims 1 to
 10. 12. An expression vector comprising the polynucleotide of claim
 11. 13. A host cell comprising the polynucleotide of claim
 11. 14. A host cell comprising the expression vector of claim
 12. 15. A pharmaceutical composition comprising the expression vector of claim
 14. 16. A method for treating a patient with a factor VIII deficiency comprising: administering to the patient in need thereof the pharmaceutical composition of claim 15 in an amount effective for treating the factor VIII deficiency.
 17. A method for expressing a human factor VIII polypeptide mutant comprising: (a) transforming a host cell with an expression vector comprising the nucleic acid of claim 12; (b) growing the host cell under conditions suitable for expressing the human factor VIII polypeptide mutant; and (c) purifying the human factor VIII polypeptide mutant from host cells expressing said mutant. 